The present invention pertains to a novel catalyst system comprising (1) a diorgano fluorophosphite ligand; (2) rhodium; and (3) a Group VIII metal, other than rhodium, or Group VIII metal-containing compound, in an amount effective to reduce the formation of HF during the use of the catalyst system. The presence of the other Group VIII metal decreases the amount of hydrogen fluoride produced during the use of the catalyst system. The hydrogen fluoride originates from very low level degradation of the ligand. The present invention also pertains to catalyst solutions of the aforesaid catalyst system and the use of the catalyst system in the hydroformylation of olefins to produce aldehydes.
Homogenous catalyst solutions prepared from transition metals and phosphorus ligands are used widely in the chemical industry. The advantages of homogenous catalysts over heterogeneous catalysts usually include higher reactivity and higher selectivity. However, homogenous catalysts often are subject to degradation and concomitant loss of activity over time. The problem of catalyst degradation is aggravated if the degradation process leads to the formation of unwanted side products that are found as contaminants in the product. Therefore, it is highly desirable to develop technologies that extend the effective catalyst lifetime, enhance selectivity and reduce contaminants in the product.
The hydroformylation reaction, also known as the oxo reaction, is used extensively in commercial processes for the preparation of aldehydes by the reaction of one mole of an olefin with one mole each of hydrogen and carbon monoxide. The most extensive use of the reaction is in the preparation of normal- and iso-butyraldehyde from propylene. The ratio of the amounts of the normal to iso aldehyde products typically is referred to as the normal to iso (N:I) or the normal to branched (N:B) ratio. In the case of propylene, the normal- and iso-butyraldehydes obtained from propylene are in turn converted into many commercially-valuable chemical products such as, for example, n-butanol, 2-ethyl-hexanol, n-butyric acid, iso-butanol, neopentyl glycol, 2,2,4-trimethyl-1,3-pentanediol, the mono-isobutyrate and di-isobutyrate esters of 2,2,4-trimethyl-1,3-propanediol. The hydroformylation of higher xcex1-olefins such as 1-octene, 1-hexene, and 1-decene yield aldehyde products which are useful feedstocks for the preparation of detergent alcohols and plasticizer alcohols. The hydroformylation of substituted olefins such as allyl alcohol is useful for the production of other commercially valuable products such as 1,4-butanediol.
Catalysts used in the hydroformylation reaction typically contain rhodium complexes comprising at least one phosphorus ligand. U.S. Pat. No. 3,239,566, issued Mar. 8, 1966, to Slaugh and Mullineaux, discloses a low pressure hydroformylation process using trialkylphosphines in combination with rhodium catalysts for the preparation of aldehydes. Trialkylphosphines have seen much use in industrial hydroformylation processes but they typically produce a limited range of products and, furthermore, frequently are very oxygen sensitive. U.S. Pat. No. 3,527,809, issued Sep. 8, 1970 to Pruett and Smith, discloses a low pressure hydroformylation process which utilizes triarylphosphine or triarylphosphite ligands in combination with rhodium catalysts. The ligands disclosed by Pruett and Smith, although used in many commercial applications, have limitations due to oxidative and hydrolytic stability problems. Since these early disclosures, numerous improvements have been made to increase the catalyst stability, catalyst activity and the product ratio with a heavy emphasis on yielding linear aldehyde product. A wide variety of monodentate phosphite and phosphine ligands, bidentate ligands such as bisphosphites and bisphosphines as well as tridentate and polydentate ligands have been prepared and disclosed in the literature. U.S. Pat. No. 5,840,647 discloses the use of diorgano-fluorophosphites, also known as fluorophosphites, as the phosphorus ligand component of hydroformylation catalysts.
It also is known that the hydroformylation catalysts suffer from the drawback that the phosphorus ligands can be decomposed by a variety of mechanisms including oxidation, acid catalyzed hydrolysis, and, in the case of certain tri-organo phosphite ligands, the rhodium-catalyzed decomposition of the phosphite as disclosed in U.S. Pat. Nos. 5,756,855 and 5,929,289. The ligand decomposition reactions are detrimental to the overall economics of the process as they result in the loss of the valuable ligand and also can result in the formation of ligand degradation products which may act as catalyst poisons. We have found that diorgano fluorophosphite compounds described in U.S. Pat. No. 5,840,647 undergo low level degradation to generate hydrogen fluoride with concomitant loss of ligand. The hydrogen fluoride contaminates the product aldehydes which is highly undesirable as it can lead to corrosion and the formation of by-products.
The present invention provides a means for the stabilization of certain homogenous catalyst systems comprising at least one diorgano fluorophosphite compound that results in the suppression of the formation of hydrogen fluoride from the catalyst systems. Thus, one embodiment of the present invention is a novel catalyst system comprising (1) a diorgano fluorophosphite ligand; and (3) rhodium; wherein the ratio of gram moles fluorophosphite ligand to gram atoms of rhodium is at least 1:1; and (3) a Group VIII metal, other than rhodium, or Group VIII metal-containing compound, in an amount effective to reduce the formation of HF during the use of the catalyst system, i.e., during the use of the catalyst to catalyze organic processes. The novel catalyst systems may be used in a wide variety of transition metal-catalyzed processes such as, for example, hydro-formylation, hydrogenation, isomerization, hydrocyanation, hydrosilation, carbonylations, oxidations, acetoxylations, epoxidations, hydroamination, dihydroxylation, cyclopropanation, telomerizatons, carbon hydrogen bond activation, olefin metathesis, olefin dimerizations, oligomerizations, olefin polymerizations, olefin-carbon monoxide copolymerizations, butadiene dimerization and oligomerization, butadiene polymerization, and other carbon-carbon bond forming reactions such as the Heck reaction and arene coupling reactions. The catalyst systems provided by the present invention are especially useful for the hydroformylation of olefins to produce aldehydes.
A second embodiment of our invention concerns a novel catalyst solution comprising (1) one or more diorgano fluorophosphite ligands, (2) rhodium, (3) a Group VIII metal, other than rhodium, or Group VIII metal-containing compound, in an amount effective to reduce the formation of HF, and (4) a hydroformylation solvent. This embodiment comprises a solution of the active catalyst in which a carbonylation process such as the hydroformylation of an ethylenically-unsaturated compound may be carried out.
A third embodiment of the present invention pertains to a hydroformylation process utilizing the above-described catalyst systems and solutions. The process of the present invention therefore includes a process for preparing an aldehyde which comprises contacting an olefin, hydrogen and carbon monoxide with a solution of a catalyst system comprising and (1) a diorgano fluorophosphite ligand, (2) rhodium and (3) a Group III metal, other than rhodium, or Group III metal-containing compound, in an amount effective to reduce the formation of HF, wherein the ratio of gram moles fluorophosphite ligand to gram atoms of rhodium is at least 1:1.